1. Field of the Invention
The present invention relates to a method for controlling the drive of an actuator of an active vibration isolation support system that includes an elastic body receiving a load from a vibrating body, a liquid chamber having a wall of which at least a part is formed from the elastic body, a movable member that moves out and back to change the capacity of the liquid chamber in a cycle, and an actuator that receives supply of current to generate an electromagnetic force for moving the movable member out.
2. Description of the Relevant Art
In order to move the movable member of this type of active vibration isolation support system out and back in response to a vibration frequency of an engine, a voltage is cyclically applied to the actuator. As shown in FIG. 6, the movable member moves out due to an electromagnetic force generated by a coil upon applying a rectangular voltage pulse to the actuator in the first half of one cycle of the out and back movement of the movable member, and the movable member moves back due to the elastic force of a return spring by stopping the application of the voltage to the actuator in the second half of the cycle. Therefore, it is possible to reduce the vibration of the engine by alternately switching on and off the voltage applied to the actuator to make the movable member move out and back.
As shown in FIG. 6, even if a rectangular voltage pulse is cyclically applied to the actuator of the active vibration isolation support system, since the current passing through the actuator changes in a sawtooth waveform with a time lag, the current might not become zero within a period when the voltage to the actuator is switched off. This might cause the generation of heat in the coil of the actuator, thus raising its temperature to increase its electrical resistance, so that a required value of current might not be obtained, and equipment surrounding the coil might be thermally damaged.